VERTICAL DISPARITY, EGOCENTRIC DISTANCE AND STEREOSCOPIC DEPTH CONSTANCY - A NEW INTERPRETATION
VERTICAL DISPARITY, EGOCENTRIC DISTANCE AND STEREOSCOPIC DEPTH CONSTANCY - A NEW INTERPRETATION
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DOI：
10.1098/rspb.1989.0059
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发表时间：
1989-09-22
期刊：
影响因子：
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通讯作者：
BISHOP, PO
中科院分区：
文献类型：
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作者：
BISHOP, PO
长期以来，一直存在一个问题，即在视觉皮质中存在双眼激活的细胞，这些细胞对垂直刺激差异具有选择性，因为通常认为只有水平差异才有助于立体深度知觉。公认的观点是，立体深度估计只相对于固定点，需要来自视网膜外来源的独立信息来衡量绝对或自我中心距离。然而，最近的理论计算表明，可以直接从垂直视差估计自我中心距离，而不需要求助于视网膜外来源。几乎没有动力用实验观察来跟进这些计算，因为通常出现在两只眼睛的图像之间的垂直差异一直被认为太小，对视觉感知没有意义，而且实验一直表明，我们对自我中心距离的有意识欣赏是相当粗暴和不可靠的。然而，立体深度恒定的真实性表明，视觉系统可以获得准确的距离信息，并且关于自我中心距离和水平视差的信息被一起处理，以便连续地重新校准不同绝对距离的水平视差值。计算表明，重新校准可以直接基于垂直差异，而不需要任何绝对距离的干涉估计。这可能在一定程度上解释了为什么我们对自我中心距离的自觉欣赏是相对粗暴的。从公布的数据中，可以计算出人类视觉系统必须能够区分的垂直差异的大小，以便深度恒定具有观察到的真实性水平。根据已发表的关于诱导效应的数据，还可以计算视觉系统检测垂直视差的阈值。这些阈值小于为实现垂直深度恒定而重新校准水平差异所需的阈值。概述了纹状皮质中双眼激活细胞的已知特性，这些特性能够区分和评估垂直差异。提出了应验证或不验证本文提出的概念的实验。
There has long been a problem concerning the presence in the visual cortex of binocularly activated cells that are selective for vertical stimulus disparities because it is generally believed that only horizontal disparities contribute to stereoscopic depth perception. The accepted view is that stereoscopic depth estimates are only relative to the fixation point and that independent information from an extraretinal source is needed to scale for absolute or egocentric distance. Recently, however, theoretical computations have shown that egocentric distance can be estimated directly from vertical disparities without recourse to extraretinal sources. There has been little impetus to follow up these computations with experimental observations, because the vertical disparities that normally occur between the images in the two eyes have always been regarded as being too small to be of significance for visual perception and because experiments have consistently shown that our conscious appreciation of egocentric distance is rather crude and unreliable. Nevertheless, the veridicality of stereoscopic depth constancy indicates that accurate distance information is available to the visual system and that the information about egocentric distance and horizontal disparity are processed together so as to continually recalibrate the horizontal disparity values for different absolute distances. Computations show that the recalibration can be based directly on vertical disparities without the need for any intervening estimates of absolute distance. This may partly explain the relative crudity of our conscious appreciation of egocentric distance. From published data it has been possible to calculate the magnitude of the vertical disparities that the human visual system must be able to discriminate in order for depth constancy to have the observed level of veridicality. From published data on the induced effect it has also been possible to calculate the threshold values for the detection of vertical disparities by the visual system. These threshold values are smaller than those needed to provide for the recalibration of the horizontal disparities in the interests of veridical depth constancy. An outlined is given of the known properties of the binocularly activated cells in the striate cortex that are able to discriminate and assess the vertical disparities. Experiments are proposed that should validate, or otherwise, the concepts put forward in this paper.